How to hide toolbar in react navigation

To hide header for only one screen do this in createStackNavigator function:

const Navigation= createStackNavigator({
  Splash: {
    screen:SplashScreen,
      navigationOptions: {
     header:null        // this will do your task
   }
  },
  Dashboard:{screen:Dashboard}
}
);

To hide header(toolbar) for all screen of createStackNavigator add

{
  headerMode:'none'
}

inside createStackNavigator. like this:

const Navigation= createStackNavigator({
  Splash: {
    screen:SplashScreen
  },
  Dashboard:{screen:Dashboard}
}
,{
  headerMode:'none'
}
);

Note : I am using createStackNavigator which may be StackNavigator for others. So if you are using StackNavigator do all this changes as i did in createStackNavigator

  static navigationOptions = {
    header: null ,
  };

this works for me

class SplashScreen extends Component {

  static navigationOptions = {
    header: null ,
  };

  render() {
    console.disableYellowBox = true;
    const { navigate } = this.props.navigation;
    return (
      ...
    );
  }
}